The invention relates to a rotatable motor vehicle mirror of a type, e.g., depicted and described in German Patent application (OS) No. 2,415,407 counterpart to U.S. Pat. No. 3,942,863.
The rotatable motor vehicle mirror type noted above has suction passages in the form of air guiding grooves in the bordering region between the shaft and the inside of the rotor bearing bore. Although the resulting air bearing and the air flow aspirated by the fan through the air guiding groove dissipates the bearing heat produced by friction and utilizes it to heat up the mirror, the bearing may overheat at high vehicle speeds or high speeds of rotor rotation. This risk can be largely excluded by the use of suitable materials for the bearing, but this in turn increases the manufacturing costs, particularly on account of the installation of bearing sleeves.
It is the object of the present invention to provide a rotatable mirror for motor vehicles which, despite simple construction of the rotor bearing, largely permits the utilization of the bearing heat to heat up the mirror, and which causes little noise during operation.
The advantages attainable by the invention especially reside in the fact that the relatively high resistance offered by the suction passageways to the oncoming air causes subatmospheric pressure at their outlet ends which aspirates additional air through the bearing clearance so that an air cushion builds up in the bearing clearance which results in low-friction and low-noise operation of the rotor. Owing to this air cushion, there is no need to use expensive bearing materials, and a plastic bearing may be employed. At the same time the air flow in the bearing clearance dissipates a substantial portion of the generated bearing heat at the place where it develops. In addition, a plurality of suction bores provided a small distance from the bearing bore contribute to the uniform dissipation of the bearing heat. Furthermore, the characterized inclined position of the blades prevents the development of noise.